should package_versions_from_directory return local or unix paths?

[wchristian]

In the fixing of #24 the question came up as to what kind of paths that function should return. I'm leaving this issue here to mark this as something needing to be decided.

@karenetheridge's input so far:

(ether) it's probably undefined (yay)
(ether) we should just figure out which way makes sense and document it
(ether) ->provides should return canonical (unixified) I think, since one of its usecases is to be stuffed into distribution metadata

[wchristian]

Notably the docs for the function say:

"This must not be used directly for CPAN META provides. See the provides method instead."